This is a new project which was initiated 4 months ago. There is clinical evidence to support that peripheral neuroepithelioma (PN) is different than classic neuroblastoma (NB) and is associated with a much more aggressive clinical behavior than the latter entity. On the other hand, the relationship of PN to Ewing's sarcoma is unknown although there is evidence to suggest that the former may be a more differentiated form of the latter in certain occasions. To evaluate the biologic behavior of these entities on an experimental basis, we will inject tumor cells of well established classic NB (CHP-126, SMS-SAN, IMR-32), PN (TC-32, TC-135, SK-N-MC, and Ewing's sarcoma (TC-71, A4573, 6647) cell lines into the subcutis and tail vein of nude mice and evaluate their tumorigenicity and metastatic potential. The morphologic differentiation of tumors before and after injection into nude mice will be evaluated as well. Preliminary results with only 2 of the cell lines (CHP-126 and TC-32) showed a slightly higher tumorigenic capacity for the PN cell line, when compared to that of classic NB (5/5 mice injected with TC-32 cells had tumor nodules vs. 3 out of 5 injected with CHP-126 cells).